git/Documentation/i18n.txt
Karsten Blees 3a59e5954e Documentation/i18n.txt: clarify character encoding support
As a "distributed" VCS, git should better define the encodings of its core
textual data structures, in particular those that are part of the network
protocol.

That git is encoding agnostic is only really true for blob objects. E.g.
the 'non-NUL bytes' requirement of tree and commit objects excludes
UTF-16/32, and the special meaning of '/' in the index file as well as
space and linefeed in commit objects eliminates EBCDIC and other non-ASCII
encodings.

Git expects bytes < 0x80 to be pure ASCII, thus CJK encodings that partly
overlap with the ASCII range are problematic as well. E.g. fmt_ident()
removes trailing 0x5C from user names on the assumption that it is ASCII
'\'. However, there are over 200 GBK double byte codes that end in 0x5C.

UTF-8 as default encoding on Linux and respective path translations in the
Mac and Windows versions have established UTF-8 NFC as de-facto standard
for path names.

Update the documentation in i18n.txt to reflect the current status-quo.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-07-01 14:55:53 -07:00

71 lines
2.9 KiB
Plaintext

Git is to some extent character encoding agnostic.
- The contents of the blob objects are uninterpreted sequences
of bytes. There is no encoding translation at the core
level.
- Path names are encoded in UTF-8 normalization form C. This
applies to tree objects, the index file, ref names, as well as
path names in command line arguments, environment variables
and config files (`.git/config` (see linkgit:git-config[1]),
linkgit:gitignore[5], linkgit:gitattributes[5] and
linkgit:gitmodules[5]).
+
Note that Git at the core level treats path names simply as
sequences of non-NUL bytes, there are no path name encoding
conversions (except on Mac and Windows). Therefore, using
non-ASCII path names will mostly work even on platforms and file
systems that use legacy extended ASCII encodings. However,
repositories created on such systems will not work properly on
UTF-8-based systems (e.g. Linux, Mac, Windows) and vice versa.
Additionally, many Git-based tools simply assume path names to
be UTF-8 and will fail to display other encodings correctly.
- Commit log messages are typically encoded in UTF-8, but other
extended ASCII encodings are also supported. This includes
ISO-8859-x, CP125x and many others, but _not_ UTF-16/32,
EBCDIC and CJK multi-byte encodings (GBK, Shift-JIS, Big5,
EUC-x, CP9xx etc.).
Although we encourage that the commit log messages are encoded
in UTF-8, both the core and Git Porcelain are designed not to
force UTF-8 on projects. If all participants of a particular
project find it more convenient to use legacy encodings, Git
does not forbid it. However, there are a few things to keep in
mind.
. 'git commit' and 'git commit-tree' issues
a warning if the commit log message given to it does not look
like a valid UTF-8 string, unless you explicitly say your
project uses a legacy encoding. The way to say this is to
have i18n.commitencoding in `.git/config` file, like this:
+
------------
[i18n]
commitencoding = ISO-8859-1
------------
+
Commit objects created with the above setting record the value
of `i18n.commitencoding` in its `encoding` header. This is to
help other people who look at them later. Lack of this header
implies that the commit log message is encoded in UTF-8.
. 'git log', 'git show', 'git blame' and friends look at the
`encoding` header of a commit object, and try to re-code the
log message into UTF-8 unless otherwise specified. You can
specify the desired output encoding with
`i18n.logoutputencoding` in `.git/config` file, like this:
+
------------
[i18n]
logoutputencoding = ISO-8859-1
------------
+
If you do not have this configuration variable, the value of
`i18n.commitencoding` is used instead.
Note that we deliberately chose not to re-code the commit log
message when a commit is made to force UTF-8 at the commit
object level, because re-coding to UTF-8 is not necessarily a
reversible operation.